Thats interesting Mark - although I don't remember the full details, we had a cat with severe eye problems from untreated infection (taken in as part of a major rescue 60+ cats and lots had eye infections). Blooming BSB
The vets worked hard on all the cats but one of the ex-breeding queens they managed clear up the infection and restored the sight. At the time they said it was like giving her her own anti-bodies to fight the infection.
So might have been the same type of thing.